Learn About Bronchiolitis

Bronchioles are small airways that connect your small breathing tubes (airways, or bronchi) to tiny air sacs of the lung. When these small airways are injured or inflamed, it is called bronchiolitis.

Key Facts

Bronchiolitis occurs when the small airways in the lung become injured or inflamed.

There are many causes of bronchiolitis, including inhaling strong irritants, infection and some medications.

Prognosis depends on the type and severity of injury.

What Is Bronchiolitis?

Bronchiolitis develops when small airways in the lungs become injured or inflamed. Inflammation can result directly from infections, medications, after bone marrow, stem cell, lung and other transplants, and related to some types of arthritis. Injury can also result from exposure to any strong irritant, such as acids and toxic fumes.

Most often, bronchiolitis is the result of a viral infection, such as respiratory syncytial virus (RSV), and is often found in young children. A second type of bronchiolitis, called bronchiolitis obliterans, is a rare and dangerous condition seen in adults. It can result in airway obstruction that can’t be reversed. Bronchiolitis obliterans is typically associated with breathing in chemicals or irritant fumes, and is sometimes referred to as popcorn lung.

How Bronchiolitis Affects Your Body

Regardless of the cause, the very small airways of the bronchioles become narrowed, and the easy passage of air is blocked. This may cause shortness of breath and cough. These symptoms may be very similar to other more common lung diseases, including asthma and chronic obstructive pulmonary disease (COPD).

How Serious Is Bronchiolitis?

Bronchiolitis is a relatively common lung condition in the United States, the most common cause being viral respiratory infections. Young children are the most commonly affected because they develop frequent respiratory infections that they may not be able to fight off as well as adults. How serious it is for any particular person depends on how severe the original injury was and how long this injury lasts. For cases related to infection, bronchiolitis often resolves without any permanent damage. If related to a toxic exposure, such as inhaling acid, some symptoms can remain present to some degree permanently. In some very specific situations, such as when bronchiolitis occurs after bone marrow or stem cell transplants, it may result in death or the need for lung transplant.